No abstract

Forty-eight Pelibuey×Katahdin male intact lambs (23.87±2.84 kg) were used in an 84-d feeding trial, with six pens per treatment in a 2×2 factorial design arrangement. The aim of the study was to evaluate the interaction of two dietary energy levels (3.05 and 2.83 Mcal/kg ME) and two dietary protein levels (17.5% and 14.5%) on growth performance, dietary energetics and carcass traits. The dietary treatments used were: i) High protein-high energy (HP-HE); ii) High protein-low energy (HP-LE); iii) Low protein-high energy (LP-HE), and iv) Low protein-low energy (LP-LE). With a high-energy level, dry matter intake (DMI) values were 6.1% lower in the low-protein diets, while with low-energy, the DMI values did not differ between the dietary protein levels. Energy levels did not influence the final weight and average daily gain (ADG), but resulted in lower DMI values and higher gain efficiencies. No effects of protein level were detected on growth performance. The observed dietary net energy (NE) ratio and observed DMI were closer than expected in all treatments and were not affected by the different treatments. There was an interaction (p<0.03) between energy and protein level for kidney-pelvic and heart fat (KPH), KPH was higher in lambs fed high energy and high protein diet but not in high energy and low protein diet. The KPH was increased (20.2%, p = 0.01) in high-energy diets, while fat thickness was increased (21.7%, p = 0.02) in high-protein diets. Therefore, it is concluded that dietary energy levels play a more important role in feed efficiency than protein levels in finishing lambs with a high-energy diet (>2.80 Mcal/kg ME). Providing a level of protein above 14.5% does not improves growth-performance, dietary energetics or carcass dressing percentage.

Sixty-four crossbred heifers (451 +/- 23 kg) were used in a 42-d feeding trial (4 pens per treatment in a randomized complete block design) to evaluate the influence of preslaughter zilpaterol hydrochloride withdrawal period on growth performance and carcass characteristics. Heifers were fed a diet based on steam-flaked corn (2.13 Mcal of NE(m)/kg). Treatments were 1) control, no zilpaterol supplementation; 2) zilpaterol supplementation for 30 d, drug withdrawn from the diet 3 d preslaughter (ZIL-3); 3) zilpaterol supplementation for 30 d, drug withdrawn 6 d preslaughter (ZIL-6), and 4) zilpaterol supplementation for 30 d, drug withdrawn 12 d preslaughter (ZIL-12). Zilpaterol was supplemented at the rate of 0.15 mg/kg of BW daily. Intake of DM averaged 9.2 +/- 0.26 kg/d and was not affected (P > or = 0.36) by treatment. Compared with control heifers, ZIL-3 increased (P < 0.01) carcass-adjusted ADG (59%), G:F (57%), apparent dietary NE(m) (31%), and decreased observed/expected DMI (25%). Treatment with ZIL-3 did not affect marbling score (P = 0.49) or backfat thickness (P = 0.17), but compared with the control group, increased HCW (3.6%, P = 0.03), carcass dressing percentage (3.2%, P = 0.02), LM area (6.3%, P = 0.05), and reduced trimmed fat (31%, P = 0.03). Prolonging the period of zilpaterol withdrawal preslaughter tended to decrease carcass-adjusted ADG (linear, P = 0.11), G:F (linear, P = 0.08), apparent dietary NE(m) (linear, P = 0.11), and carcass dressing percentage (linear, P = 0.11). We conclude that growth performance and carcass yield responses to zilpaterol supplementation are negatively affected by prolonging the period of zilpaterol withdrawal beyond 3 d (the required minimum withdrawal period according to label). Drug withdrawal period may be a relevant factor in explaining variation in performance response to zilpaterol supplementation in commercial feedlots.

No abstract

Robles-Estrada, J.C., Barreras-Serrano, A., Contreras, G., Estrada-Angulo, A., Obregdn

Objective: To determine the prevalence and the risk factors associated to the incorrect application of the anabolic implant in intensive cattle feedlots. Design/Methodology/Approach: An observational study was conducted in which 888 cattle ears were evaluated from five livestock feedlots. The criteria of the condition of the anabolic implant were: correct and incorrect (encapsulated, abscessed, in cartilage, badly placed, heaped, partial and absent). The results were evaluated through the chi-squared test and logistic regression, the alpha level established was 0.05. Results: A prevalence of 64.30% incorrectly applied anabolic implants was observed. At least 50% of the cattle from the feedlots evaluated presented faults in the application of the implant. Encapsulated and badly placed implants represented 91.6% (51.4 and 40.2%, respectively) of the total incorrect conditions. The risk of a bovine presenting an incorrect condition increased 1.8 times more when the feedlot has more than 4000 cattle (P<0.001) and 4.2 times more when they are females (P<0.001); the season of the year was not a risk factor (P>0.17). Study Limitation/Implications: The incorrect application of anabolic implants derives in faults that complicate their absorption and integration into the organism, which is why more studies are suggested to determine the economic impact that this can cause. Findings/Conclusions: The prevalence of the fault in anabolic implants is high, and, therefore, the productive and economic benefits that favor the application of this productive technology are not being obtained, in addition to there being determinant risk factors.

No abstract

El objetivo fue determinar composición nutricional y digestibilidad in situ del residuo industrial de té de jazmín. Se realizó análisis químico proximal, se determinó fibra detergente neutra (FDN) y ácida (FDA), energía metabolizable (EM), neta de mantenimiento (ENm) y ganancia (ENg) y taninos, digestibilidad in situ y cinética de degradación durante 0, 3, 6, 12, 18, 24, 36, 48, y 72 h. Se observó 20.19% PC, 30.5% FC, 65.61% FDN, 49.01% FDA, 1.47 mg g−1 y taninos condensados y 3.21 mg g−1 de hidrolizables, 2.04 Mcal kg−1 EM, 1.19 Mcal kg−1 ENm y 0.74 Mcal kg−1 ENg. La degradación de MS fue 50.63% a la hora 72, PC mostró degradación de 17.5%, los parámetros de cinética de degradación para la MS fueron a = 4.73, b = 48.66 y c = 0.05. El residuo de té de jazmín es una opción viable como fuente de fibra en la dieta de rumiantes